Adjustable tappet for overhead-camshaft internal combustion engines

ABSTRACT

A valve tappet arrangement for an overhead camshaft internalcombustion engine including a tappet-setting member adapted to be inserted into an opening in the valve tappet for adjusting the effective thickness of the tappet, the tappet setting member being in the form of a self-locking pallet so that when it is fully inserted into position in the valve tappet it is locked against direct withdrawal from the valve tappet.

United States Patent Inventor Royston Gordon Freese Upper Beedlng, England Appl. No. 842,103 Filed July 16, 1969 Patented Aug. 17, 1971 Assignee Ricardo & Co., Engineers, (1927) Limited Priority July 22, 1968 Great Britain ADJUSTABLE TAPPET FOR OVERHEAD- CAMSIIAFT INTERNAL COMBUSTION ENGINES S-CIaims, 5 Drawing Figs.

U.S.Cl l23/90.27, 74/569, 123/90.52

1nt.Cl F01l1/l4, F011 1/20 Field of Search [56] References Cited UNITED STATES PATENTS 2,863,432 12/1958 OBrien 123/90 3,025,841 3/1962 Beckham 123/90 Primary ExaminerAl Lawrence Smith AttorneyWat son, Cole, Grindle & Watson mimemummn 3.599.613

INVENTOR Rows-rm G F1519:

ATTORNEY concerned with a valve tappet arrangement for an overhead camshaft engine.

The present invention is adevelopment of the invention forming the subject of US. Pat. application, Ser. No. 788,761 assigned to the assignees of the present application and now abandoned.

According to one aspect of the present invention a valve arrangement overhead camshaft internal-combustion engine, comprises a valve tappet adapted to be interposed between a cam and a valve stem, and a tappet-setting member adapted to be inserted into an opening in the valve tappet, the said setting member beingjn the form of a pallet having a tappet face which is arranged, when the pallet is inserted in the valve tappet opening, 'to be in operative relationship to the end of the valve stem to set a predetermined minimum distance between the end of the valve stem and the cam surface, the pallet also being provided with locking means in the form of at least one abutment disposed on one side of the said tappet surface, which abutment, in the fully inserted position of the pallet, lies adjacent the side of the valve stem to prevent withdrawal of the pallet from the valve tappet past the valve stem.

' According to another aspect of the present invention a valve arrangement for an overhead camshaft internal-combustion engine, comprises a valve tappet adapted to be interposed between a cam and a valve stem, and a tappet-setting member adapted to be inserted into an opening in the valve tappet, the said setting member being in the form of a rodlike pallet which is rotatable about its longitudinal axis and has a tappet face'which is arranged, when the pallet is fully inserted in the valve tappet opening, to be in operative relationship to the end of the valve stem to set a predetermined minimum distance between the end of the valve stem and the cam surface, the pallet also being provided with locking means, and the pallet being insertible at least partially into the valve tappet without engaging the end of the valve stem, and thereafter the pallet being rotatable to bringits said tappet face into operative-relationship with the end of the valve stem and to operate the locking means to lock the pallet against direct withdrawal from the valve tappet.

Preferably the spacing member isprovided with an abutment arranged to lie on one side of the valve stem in the locked position to prevent direct withdrawal of the spacing member. The latter is preferably also provided with cam means for depressing the valve stem against the action of the valve spring, so as to facilitate the insertion of the spacing member into the locked position.

The opening to receive the spacing member is conveniently in the form of a through bore intersected by the valve stem and the spacing member may be in the form of a short rodlike pallet, with preferably two abutments of cylindrical form arranged respectively on each side of the said tappet face, which abutments constitute the locking means referred to.

The pallet is preferably also provided at one end with a relieved face which may lie parallel to and on the same side as the said tappet face, the relieved face being arranged so that it lies over the valve stem when the pallet is partially inserted into the tappet'ln this position the bar pallet can be rotated so that the edge of the relieved face acts as a cam which depresses the valve stem against the action of the valve spring. Thus, when the valve stem has been depressed to the fullest extent that rotation of the pallet will produce, the pallet can then be moved further into the bore until the tappet face lies in position above, but facing away from the end of the valve stem. The pallet is then rotated until the tappet face lies in position to engage the end of the valve stem, the end of the valve stem being biased against the tappet face by the valve spring between the abutments formed on either side of the tappet face thereby to lock the pallet against withdrawal in either direction along the bore.

The invention may be carried into practice in various ways and one specific embodiment will now be described by way of example with reference to the accompanying drawings, in which:

FIG. 1 is a diagrammatic cross section through a valve tappet arrangement according to the present invention, with a pallet partially inserted into the tappet and in the first stage of insertion, I

FIG. 2 is a perspective view of the pallet, and

FIGS. 3 to 5 are views similar to FIG. 1 showing the progressive stages of the insertion of the pallet into the valve tappet, the valve spring and retaining arrangement being omitted for clarity.

As shown in FIG. 1 the tappet comprises an upper part 1 arranged to be engaged by a cam 2 on an overhead camshaft 3 and a lower cup-shaped part 4 the exterior of which is arranged to slide in tappet guides 5. The interior of the cupshaped part 4 receives the upper end of a valve stem 6 having an annular groove 7 for retaining split cotters 8 surrounded by a valve cup 9 against which engages the end of the valve spring 10 all in conventional manner.

The tappet is provided with a through bore 12 extending diametrically across it, the wall of the bore opening at its lower side 13 into the interior of the cup-shaped lower part 4 of the tappet so that the top of the valve stem 6 projects into the bore 12. The bore 12 receives a pallet 14 shown more clearly in FIG. 2, the pallet 14 having one end portion 15 of full cylindrical form, an intermediate part 16 of part cylindrical form, the remainder of the surface of the part 16 being formed as a flat face 17 parallel to the axis of the pallet, a second intermediate part 18 of full cylindrical form and an end portion 20 of part cylindrical form the remainder of the surface of which part 20 is formed as a second flat face 21 which is parallel to the axis of the pallet terminating in one end 22. The thickness of the bar pallet is greater at the flat face 17 than at the flat face 21 and the flat face 17 and the flat face 21 are arranged parallel to one another.

In use the end 22 of the pallet is first inserted into the bore 12 with the flat face 21 facing away from the cam 2 until the abutment 23 formed between the flat face 21 and the part 18 of full circular cross section abuts against the side of the end of the valve stem 6, the flat face 21 lying above the top of the valve stem, as shown in FIG. 1. The pallet is then rotated about its longitudinal axis through in either direction by means of a screwdriver inserted into a slot 24 in its end, so that one edge of the face 21 bears against the end of the valve stem thereby depressing the valve stem 6 against the bias of the spring 10 by a camming action so that its end is moved into a position parallel to the wall of the bore, as shown in FIG. 3. The pallet is then moved axially further into the bore 12 until the flat face 17 lies above and facing away from the valve stem 6 the part 16 of the pallet engaging the end of the valve stem in this position, as shown in FIG. 4. The pallet is then rotated again through 180, again in either direction, so that the end of the valve stem 6 contacts the flat face 17 between the abutments formed by the parts 15 and 18 of full circular cross section, as shown in FIG. 5. The pallet in this position is thus locked against direct withdrawal from the tappet and it cannot be withdrawn, until it is rotated through 180, and by virtue of the pressure exerted on the flat face 17 by the end of the valve stem 6 the pallet will not become inadvertently rotated by vibration during operation of the engine.

It will be appreciated that the thickness of the part 16 determines the setting of the distance between the end of the valve stem 6 and the surface of the cam 2 and hence the tappet clearance, and a set of pallets can be provided each having different thicknesses so that the one giving the required tappet clearance can be selected, according to the adjustment required.

What we claim as our invention and desire to secure by Letters Patent is:

1. A valve tappet arrangement for an overhead-camshaft intemal-combustion engine comprising a valve tappet interposed between a rotary cam and one end of the stem of a poppet valve for cyclic actuation of the valve by the rotation of the valve cam, the valve stem being biased towards the valve cam by valve spring means, and the tappet having a throughbore opening therein extending transversely to the valve stem,

and a rodlike pallet insertible longitudinally in said throughbore opening and is turned into an operative position with the tappet-setting surface facing the end of the valve stem, the tappet-setting surface sets a predetermined minimum distance between the end of the valve stem and the valve cam and the locking abutments lie one on either side of the end of the valve stem to prevent withdrawal of the pallet in either direction along the through-bore opening, and in which the pallet is also formed with a camming portion adapted to bear against the end of the valve stern with a camming action to depress the valve stem against the action of the valve spring means in response to rotation of the pallet in the said opening during its insertion.

2. A valve tappet arrangement as claimed in claim 1, wherein the pallet is provided at one end with a'relieved face, said relieved face being arranged to overlie the end of the valve stem in spaced relationship therewith when the pallet is partially inserted into the valve tappet.

3. A valve tappet arrangement as claimed in claim 2, wherein the said relieved face is planar and lies parallel to the axis of the pallet, an edge of said relieved face constituting said camming portion whereby rotation of the partially inserted pallet causes the valve stem to be cammed to its depressed condition by said edge.

4. A valve tappet arrangement as claimed in claim 3, wherein the said tappet-setting surface is planar and is parallel to the said relieved face, said tappet-setting surface and said relieved face being formed in the same flank of the pallet.

5. A valve tappet arrangement as claimed in claim 4, wherein the said tappet-setting surface and the said relieved face' are axially spaced from each other along the pallet, whereby after the partially inserted pallet is rotated to cam the valve stem to its depressed condition; the pallet is then capable of being further inserted into the valve tappet and further rotated into its operative position with the said tappet-setting surface engaged with the end of the valve stem and with the locking abutments on either side of the end of the valve stem. 

1. A valve tappet arrangement for an overhead-camshaft internalcombustion engine comprising a valve tappet interposed between a rotary cam and one end of the stem of a poppet valve for cyclic actuation of the valve by the rotation of the valve cam, the valve stem being biased towards the valve cam by valve spring means, and the tappet having a through-bore opening therein extending transversely to the valve stem, and a rodlike pallet insertible longitudinally in said through-bore opening as a tappet-setting member interposed between the tappet and the end of the valve stem, the pallet being rotatable in said throughbore opening about its longitudinal axis and being formed on one flank with a tappet-setting surface and with a pair of axially spaced locking abutments located one on either side of said tappet-setting surface, whereby when the pallet is fully inserted into said through-bore opening and is turned into an operative position with the tappet-setting surface facing the end of the valve stem, the tappet-setting surface sets a predetermined minimum distance between the end of the valve stem and the valve cam and the locking abutments lie one on either side of the end of the valve stem to prevent withdrawal of the pallet in either direction along the through-bore opening, and in which the pallet is also formed with a camming portion adapted to bear against the end of the valve stem with a camming action to depress the valve stem against the action of the valve spring means in response to rotation of the pallet in the said opening during its insertion.
 2. A valve tappet arrangement as claimed in claim 1, wherein the pallet is provided at one end with a relieved face, said relieved face being arranged to overlie the end of the valve stem in spaced relationship therewith when the pallet is partially inserted into the valve tappet.
 3. A valve tappet arrangement as claimed in claim 2, wherein the said relieved face is planar and lies parallel to the axis of the pallet, an edge of said relieved face constituting said camming portion whereby rotation of the partially inserted pallet causes the valve stem to be cammed to its depressed condition by said edge.
 4. A valve tappet arrangement as claimed in claim 3, wherein the said tappet-setting surface is planar and is parallel to the said relieved face, said tappet-setting surface and said relieved face being formed in the same flank of the pallet.
 5. A valve tappet arrangement as claimed in claim 4, wherein the said tappet-setting surface and the said relieved face are axially spaced from each other along the pallet, whereby after the partially inserted pallet is rotated to cam the valve stem to its depressed condition, the pallet is then capable of being further inserted into the valve tappet and further rotated into its operative position with the said tappet-setting surfaCe engaged with the end of the valve stem and with the locking abutments on either side of the end of the valve stem. 